In the earliest videoconference, people interact with each other through images and sounds only. Later, the H.261 protocol enables participants of the videoconference to transfer a static graphic file of a 4CIF size through a motion video channel so that the participants can share slides with each other. However, the sharing is implemented by contending for the motion video channel. The resolution of the slides is not high, and the transmission of slides tends to cause a pause of motion videos.
Later, the H.239 protocol enables participants to create an H.239 auxiliary stream channel to transmit slides exclusively and use a mainstream channel to transmit motion videos. Therefore, no mutual impact exists between transmission of motion videos and transmission of slides. A typical application scenario is shown in FIG. 1. A conference terminal 12 receives a conference image taken by a camera 11 and a file (such as a PPT or Word file) of a computer 10 simultaneously, and performs video encoding for the conference image and the file (generally based on the H.263 or H.264 protocol). Afterward, through a channel provided by the H.239 protocol, the conference terminal 12 sends the two video streams to a Multipoint Control Unit (MCU) 13 simultaneously, and the MCU 13 forwards the video streams to another terminal 14 in the conference. After receiving the two video streams, the terminal 14 decodes them to obtain two different streams of video images, and displays them on a projector 16 or a TV set 15. In this way, any participant can share files with all other participants, and simple data exchange is realized. However, a noticeable drawback of this mode of sharing slides is: The participants cannot interact with each other. When a speechmaker expounds the slides, other participants watch the slides but cannot make marks on the slides, which reduces the discussion efficiency and deteriorates interactivity.
In view of the drawback, another solution is put forward in the conventional art to enable the interaction between participants of the videoconference by means of making marks on an electronic whiteboard. As shown in FIG. 2, an electronic whiteboard server 20 is deployed on the conference server side, and an electronic whiteboard client is deployed on each videoconference terminal, for example, client 21, client 22, client 23, client 24, and client 25. Such clients are generally Personal Computers (PCs), and some clients may be conference servers or conference clients in the conference subsystem. All clients are connected to the electronic whiteboard server 20 through a network. The electronic whiteboard server 20 starts an electronic whiteboard, which may be a blank background. Alternatively, a picture or a slide may be used as the background. The electronic whiteboard server 20 sends the content on the electronic whiteboard to all clients in the form of pictures. Therefore, each client can see the same content, and the participant can make marks on the electronic whiteboard through the client, for example, draw lines or circles or input texts on the electronic whiteboard. Such operations are transmitted onto the electronic whiteboard server 20. After receiving the operations performed by the client, the electronic whiteboard server 20 updates the content of the electronic whiteboard, and sends the updated content to all clients. In this way, all participants share the whiteboard to have a discussion. However, this mode is restricted in the scope of use. For example, a user is unable to mark a slide directly, namely, the system is unable to share a marked slide. Besides, the system needs to create another electronic whiteboard system, and at least one computer needs to be configured on each conference site, which increases the system complexity and the construction costs.
In the conventional art, another method, namely, remote collaboration, is similar to the method of marking the electronic whiteboard. As shown in FIG. 3, the system includes a remote collaboration server 30; and a computer is configured for each videoconference site, for example, computer 31, computer 32, computer 33, and computer 34. Such computers are connected with the remote collaboration server 30 through a network. On a conference site which needs to share its desktop with other participants, a remote collaboration server is started, and the computer desktop image (such as a PPT or Word file) of this conference site is shared with all other participants. After being connected to the remote collaboration server 30 through a local computer, the participants of other conference sites can see the computer desktop offered by the remote collaboration server 30 for sharing. At the same time, the operations performed through the local mouse and keyboard are transmitted to the remote collaboration server 30. Therefore, all participants can operate the same application such as a PPT or Word jointly. However, this system also involves an extra remote collaboration system, and at least one computer needs to be configured for each conference site, which increases the system complexity and the construction costs. Moreover, special remote collaboration parameters need to be configured on each computer of each conference site, and a user needs to operate two systems, for example, a shared remote system and a local system. The files such as PPT and Word files for sharing need to be copied into the computer of the conference site beforehand, and the plug-and-play feature available on a notebook computer cannot be realized, which leads to inconvenience of operations.
Therefore, at least the following problems exist in the conventional art:
In a videoconference system, when participants exchange data, the interactive data offered by the videoconference system in the conventional art to the participants is restricted. For example, in a system with electronic whiteboards, slides cannot be marked. Moreover, the videoconference systems such as electronic whiteboards are complicated and costly.